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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A114572 Number of "ultrasweet" Boolean functions of n variables which depend on all the variables.

Original entry on oeis.org

2, 1, 2, 6, 27, 185, 2135, 55129
Offset: 0

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Author

Don Knuth, Aug 17 2008, Oct 14 2008

Keywords

Comments

Inverse binomial transform of A114491.
This sequence enumerates a certain type of matroid, except for the first entry (which is 2 instead of 1). If the first entry is changed from 2 to 1, giving A118085, this enumerates "combinatorial geometries" on n labeled points.
These are matroids in which no element has rank 0; equivalently, all one-element sets are independent; equivalently, the closure of the empty set is empty.
These are called "simple matroids" in A002773. So A118085 is the "labeled" equivalent of that sequence, which counts unlabeled points.

Examples

			For all n>1, a function like "x2" is counted in A114491 but not in the present sequence.

Crossrefs

Cf. A114302, A114303, A114491, A118085, A002773.
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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